linux-kernel - Re: [PATCH 1/2] mm/PAGE_IDLE_FLAG: Set PAGE

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Date:   Fri, 6 Aug 2021 19:01:45 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     SeongJae Park <sj38.park@...il.com>, akpm@...ux-foundation.org
Cc:     SeongJae Park <sjpark@...zon.de>, broonie@...nel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-next@...r.kernel.org, mhocko@...e.cz,
        mm-commits@...r.kernel.org, sfr@...b.auug.org.au,
        willy@...radead.org, linux-damon@...zon.com
Subject: Re: [PATCH 1/2] mm/PAGE_IDLE_FLAG: Set PAGE_EXTENSION for none-64BIT

On 8/6/21 2:51 AM, SeongJae Park wrote:
> From: SeongJae Park <sjpark@...zon.de>
> 
> Commit 128fd80c4c07 ("mm/idle_page_tracking: Make PG_idle reusable") of
> linux-mm[1] allows PAGE_IDLE_FLAG to be set without PAGE_EXTENSION
> while 64BIT is not set.  This makes 'enum page_ext_flags' undefined, so
> build fails as below for the config (!64BIT, !PAGE_EXTENSION, and
> IDLE_PAGE_FLAG).
> 
>      $ make ARCH=i386 allnoconfig
>      $ echo 'CONFIG_PAGE_IDLE_FLAG=y' >> .config
>      $ make olddefconfig
>      $ make ARCH=i386
>      [...]
>      ../include/linux/page_idle.h: In function ‘folio_test_young’:
>      ../include/linux/page_idle.h:25:18: error: ‘PAGE_EXT_YOUNG’ undeclared (first use in this function); did you mean ‘PAGEOUTRUN’?
>         return test_bit(PAGE_EXT_YOUNG, &page_ext->flags);
>      [...]
> 
> This commit fixes this issue by making PAGE_EXTENSION to be set when
> 64BIT is not set and PAGE_IDLE_FLAG is set.
> 
> [1] https://github.com/hnaz/linux-mm/commit/128fd80c4c07
> 
> Fixes: 128fd80c4c07 ("mm/idle_page_tracking: Make PG_idle reusable")
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: SeongJae Park <sjpark@...zon.de>

Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested

Thanks.

> ---
>   mm/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index d0b85dc12429..50ca602edeb6 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -741,6 +741,7 @@ config DEFERRED_STRUCT_PAGE_INIT
>   
>   config PAGE_IDLE_FLAG
>   	bool "Add PG_idle and PG_young flags"
> +	select PAGE_EXTENSION if !64BIT
>   	help
>   	  This feature adds PG_idle and PG_young flags in 'struct page'.  PTE
>   	  Accessed bit writers can set the state of the bit in the flags to let
> @@ -749,7 +750,6 @@ config PAGE_IDLE_FLAG
>   config IDLE_PAGE_TRACKING
>   	bool "Enable idle page tracking"
>   	depends on SYSFS && MMU && BROKEN
> -	select PAGE_EXTENSION if !64BIT
>   	select PAGE_IDLE_FLAG
>   	help
>   	  This feature allows to estimate the amount of user pages that have
> 


-- 
~Randy